Designing Kitchens and Bathrooms - Gurgling Whirlpool Tub

I put an addition on my house with a new master bath. I have a 2" vent going up from the bathroom, right behind the toilet, but it is about 5 feet from the whirlpool tub. Everything had passed inspection. When the whirlpool tub is draining, I hear the gurgling sound out of the overflow. If the tub is totally filled and starts draining, there is no gurgling. When the tub drains to about 1/2 full, the gurgling starts and doesn't stop until it is empty. Everything is fine with the shower and toilet. Is there anything I can do now that all the walls are closed up?

What you may be hearing is regirgitation from the piping used for recirculation of water. When the tub is full, these holes are covered by water, but when the water gets below them, the water in them is trying to get out, and can't, because the piping goes down toward the pump unit. Your situation may be different, but I have seen it in another installation with similar conditions. With a piece of tubing held to your ear, put the other end near one of these recirculation openings while it is draining to see if that is the case.

Chandler is right on... My whirlpool is exactly the same....... to eliminate the sounds from bothering me.... I leave the bathroom when the tub is draining..... :o